Step 1: Create the form you want to add to your template. You can follow these steps to see how to create a form.
Step 2: Once you have created the form, go to the left menu and click on "Lead Generation" > "Landing Pages". Then, create a new landing page following this guide.
Step 3: On the landing page, insert the form you created earlier. Find instructions on how to do this here.
Step 4: After inserting the form on the landing page, go back to the left menu and select "Campaigns Manager" > "Email Templates". Select the template where you want to link the form.
Step 5: In that template, you can add a button that directs to the landing page containing the form.
To do so, go to the right side of the screen and, from the content column, select the button option and drag it into your template.
Step 6: Click on the button, and in the right column, click on "Custom Links".
Step 7: After clicking it, a pop-up window will appear. Select the option "Landing Page URL".
Step 8: Select the landing page where you have included your form.
You're all set! You have now added a form to an email template.